This just started happening to me yesterday (and has been reproduced): if I start to edit a post on a site where I have edit privileges, which means I'm using the inline editor, then the edit cursor is positioned at the end of the post instead of the beginning. On the other hand, if I start to edit on a site where I don't have such privileges, which means the site loads a new page for editing, the cursor is positioned at the beginning where I expect it.
Some test cases:
- Edit any post on a site where I have the edit privilege: inline editor, cursor at end.
- Edit my own post on a site where I don't have the edit privilege (but you can always edit your own posts): new page, cursor at beginning.
- Edit any post while not logged in: new page, cursor at beginning.
I'm using Firefox 51.0.1 on Windows 7. Two other people have reproduced this in Firefox (specifics unknown). We don't yet have observations for other browsers.
(Thank you TL denizens for help in characterizing this bug.)